Control apparatus



rm w M ENCE EXAMINER FIP8Z12 XR 2,262,790

Nov. 18, 1941.. R. D. BEAN EI'AL 2,262,790

' CONTROL APPARATUS Filed Aug. 2, 1940 2 Sheets-Sheet 1 FIG. 5. ROSCOE o. BEAN HARRY S. JONES ATTORNEY 2 5 0 2 O 1 CROSS REFERENCE EXAMINER Nov. 18, 1941. R. D. BEAN ETAL 2,262,790

CONTROL APPARATUS Filed Aug. 2, 1940 Sheets-Sheet 2 FIG 3 74 INVENTOR.

ROSCOE D. BEAN 1 HARRY S. JONES Patented Nov. 18, 1941 UNITED STATES PATENT OFFICE CONTROL APPARATUS Roscoe D. Bean, Ambler, and Harry S. Jones,

Philadelphia, Pa" asslg'norl to The Brown Instrument Company, Philadelphia, Papa corporation of Pennsyl Application August 2, 1940, Serial No. 30,994

The present invention relates to automatic control apparatus, and more particularly, to automatic control apparatus of the follow-up type which is adapted to effect proportional control of the supply of a condition varying agent in response to the fluctuations of a variable condition to maintain said condition at a predetermined, desired value.

An object of the invention is to provide automatic control apparatus-of the type referred to above wherein the primary controlling element is a highly sensitive and delicate device for effecting whose actuation only very weak forces are available.

Another object of the invention is to provide automatic control apparatus of the type referred to above wherein the primary controlling element is a highly sensitive device having a dellcate actuating member, and wherein adjustments of the controlled device for regulating the supply of condition varying agent are effected in response to actuation of said delicate actuating member without retarding the movement of the latter and thereby reducing the sensitiveness of the primary controlling element. By imposing no work on the primary controlling element, precision of its actuation is insured.

A further object of the invention is to provide automatic control apparatus of the type referred to above wherein the primary controlling element is a highly sensitive device of extremely delicate nature, and wherein the means controlled thereby for effecting adjustments in the supply of condition varying agent is a rugged power driven device for which full driving power is available on small changes in the actuation of said primary controlling element.

A specific object of the invention is to provide automatic temperature control apparatus of the follow-up type which is adapted to eflect stepless or proportional control of the supply of a temperature varying agent under control of a highly sensitive measuring device, such, for example, as a pyrometer responsive to the temperature variations of a region whose temperature it is desired to maintain constant and for effecting whose actuation only a weak electric I current is available.

A still further object of the invention is to provide automatic control apparatus of the type referred to above which is relatively simple and rugged in construction.

In the prior art, automatic control devices adapted to efiect stepless or proportional regulations of the supply of a condition varying agent in accordance with the extent of deflection of a primary controlling element have been limited to arrangements wherein the primary controlling element is quite rugged and where considerable power for the operation of that element is available, or have been limited to arrangements wherein only a small fraction of full power for the controlled device which effects adjustments in the supply of condition varying agent is available on small changes in the actuation of the primary controlling element. In accordance with the present invention full power for the controlled device which adJusts the supply of condition varying agent is available on small changes in the actuation of a primary controlling element, the latter of which may be extremely sensitive and delicate in nature.

In the preferred form of the invention, provisions are included for readily effecting a so-called throttling range" adjustment whereby the extent to which the controlled device or fuel valve is adjusted in response to a givenchange in furnace temperature or other control quantity may bevaried.

The preferred form of the invention also includes provisions for effecting a so-called reset" adjustment whereby on a change in an operating condition, such, for example, as a change in the load on a furnace which is being controlled to minimize variations in the furnace temperature, the tendency of the furnace load or other operating condition to increase or decrease the furnace temperature or other condition under control may be neutralized.

The invention disclosed and claimed herein is of especial utility for use in an automatic control system in which the value of the condition under control is measured by a sensitive galvanometer, having a delicate deflecting member, constituting the primary controlling element of the control system.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated a preferred embodiment of the invention.

Of the drawings:

Fig. 1 is a diagrammatic representation of a preferred embodiment of our invention;

Fig]. 2 is a top view of the optical system of Fig. 2

Fig. 3 is a preferred structural view of the optical system of Fig. 1;

Fig. 4 is a detail view of a portion of Fig. 3; and

- Fig. 5 illustrates a modification of the Fig. 4 arrangement.

value of any variable condition such as tempermore particularly, interioroiamrnace i towhichathermocouplc supplyofheatingagentor iscontroiiedbyavaivc2 of a suspension type galvanometer indicated generalLvatI. Thegalvanometeriisahighlysensitive measuring instrument capable of responding to extremely weak electric current iiows in the conductors 4 and 2, and is utilized in accordance with our invention to control the selective and thereby-controls control is; 7 turn, controls motor r d. valve 2 and also-9W designatedfat it, ant I in which is connected by a piimanfifitojaicrank disc 12 carried by the shaitaoi m ter agivm'cn shaft is indicated bath dotted The metershaft is operatedthrough 'ai (not shown) by motorjrotor'ld'. fiflfherotprgil -is selectively controlled for} rotationiingone tion or the other by g 5 windings its, and it..-

aaeaveo switch blade is moved into engagement with the contact 21 or 22, respectively.

Electrical power is adapted to be supplied the reversible motor I through the switch blade 2i and contacts 26 and 21 of relay 2 from alternatingcurrentsupplyconductorsUandU. As illustrated. the right ends at the field windings II and it of motor I are connected together and to the supply conductor 1). The other end of 21 and the other connected to the contact 22. The switch blade 22 oi relay 2 is connected to the supply conductor 11' so that on deflecflon of the switch blade into engagement with the contact 22. energizing current is supplied the field winding II to produce rotation of the rotor II in one direction, and on deflection of the switch blade into engagement with the contact 21, energizing current is supp ied the field winding II to produce rotation of the rotor It in the opposite direction.

Electric power is supplied the relay 2 under control of the circuit I, referred to hereinbefore, from the high voltage secondary winding 22 a transformer 22 having a line voltage primary winding 22 connected to the alternating voltage supply conductors L and L. and secondary -wimiings 2|, 22, 22, and 24. To this end the iowerterminalsotrelaycoils "and 2lare connected together and are connected by a common conductor 2! to the right end terminal of the secondary winding 22. The upper terminal oi relay coil I2 is connected to a tap 22 intermediate it thr ugh a circuit whichmay be traced from said upper terminal to ya conductor 21. the anode to cathode resistance so! the triode section A 01 a twin type electronic the arrangement being such-'thaii when jthe field winding I is energized. wil ie -{is lidjustedtowards its open position, andwhen'j'only the ileld winding ii is energized, the valve 2 is moved toward its closed position.

Theshai'tofmotoriisalso nected with a contact ll which is in engagement with a slidewire resistance l2, and is adapted to adjust that contact along the length of the resistance It whenever it operates to adjust the position of valve 2. The contact i1 and alidewire resistance It are connected in the follow-up arrangement ll referred to hereinbefore, and for convenience will hereinafter be referred to as the follow-up potentiometer. Whenthe valve 2 is adjusted toward its open position. the contact i1 is moved toward the right.

The relay generally designated at 8 includes apairof coils i9 and2fl whicharedisposedin operative relation with a balanced armature 2|. Armature 2| is pivoted for rotation at 22, a point intermediate its ends, and carries an iron core 22 at one end, which core is adapted to move into and out of coil it, and carries an iron core 24 at the other end. which core is adapted to move into and out of the coil 22. Armature 2i also carries a switch blade 25 which is disposed between a pair of stationary contacts 26 and 21. When the coils i9 and are equally energized, the switch blade is held intermediate and out of engagement with both of the contacts 26 and 21, but when one of the coils it or 22 is energized to a greater extent than the other.

ciperatively con- "valve 22 which also includes a triode section B, a conductor 22 to a tap ll, which is adjustable by u knob along a slidewire resistance 42, resistance'l2. anda conductor 42 to the tap 26 on transformer secondary winding 22. the transformer secondary winding 22 is con- As shown,

nected across the terminals of the resistance 42.

It is noted the portion of the secondary winding 22 to the left of the tap 22 is so wound with respect to the rest of the winding and with respect to the secondary winding 22 that the polarities of the voltages during one half cycle are as shown. The upper terminal of relay coil 22 is connected to the tap 22 on winding 22 through a circuit including a conductor ll. the anode to cathode resistance of the triode B of valve 22, the conductor 22. tap ll, resistance 42, and conductor l2.

When the triode sections A and B of valve 22 are equally conductive, the relay coils l2 and 22 are energized to the same extent and consequently the relay switch arm 25 will be held in an intermediate position out of engagement with both of the contacts 26 and 21, but when one triode section A or B is more conductive than the other, the relay coil I! or 20 will be energized to a greater extent d p nding upon which triode section is more conductive.

cathode SI and a heating filament 52. The heating filaments 42 and 52 may be connected in parallel as shown and receive energizing current through conducting leads, not shown in order not to confuse the drawings, from the transthe former secondary winding 24. Anode voltage is QUU supplied the triode sections A and B through the energizing circuits traced above for the relay coils l8 and 20. l

The grid circuit for the triode A may be traced from the grid 46 to a conductor 53, in-which a current limiting resistance 54 is inserted to the left end terminal of winding 28, tap 38, conductor 43. resistance 2, tap l0, and conductor 39 to the cathode 47. It is noted the winding 12 and the portion of winding 28 to the left of tap 36 are so phased as to oppose each other, the winding 32 tending to render the grid 46 negative with respect to cathode 41 during the half cycle when the anode 45 is positive and the portion of winding 28 referred to tending to render the grid 46 positive with respect to cathode 41 during that same half cycle. Whether the grid 46 is at the same potential as cathode 41 or positive or negative with respect thereto is determined by the adjustment of contact 40 along resistance 42. It is noted the potential of grid 46 is substantially constant during the normal operation of the system.

The grid circuit of the triode B may be traced from the grid 50 to a conductor 55, in which a' current limiting resistance 56 and a resistance 51 shunted by a condenser are inserted, to the resistance 2, tap 40 and conductor. 3 9.:to the cathode 5|. The potential of grid "relatively lto cathode 5! is adapted to be varied in accordance with the illumination of a photoelectric; cell h 59. The photoelectric cell 59 may desirably .b'efa-fi of the electron emissive type and is between the right end terminals of transformer.- s

secondary winding 28 and resistance )1; {The- 5 current conducted by cell 59 passesthrough re f: sistance 51 so that a potential drop is establish d. across the latter, the-magnitude or, which-po tential drop depends uponpthe illuminationofunuoo ritr tiitliiil:

EMMFR carried by the movable coil thereof as illustrated tically in Fig. 1 and in more detail in Fig. 3 which is a preferred embodiment of our invention. An index I which is disposed in cooperative relation with a scale I! is mounted on the end of pointer I.

As illustrated in Fig. 3, the galvanometer 0 includes a U-shaped permanent magnet II provided with pole faces 64 and l between which the movable coil of the galvanometer is suspended by a suspension wire (not shown) in a well-known manner. A light aluminum vane 08 which is impervious to light is disposed on the end of the pointer 80. The salvanometer t is so arranged with respect to the photoelectric cell 59 and with respect to a source of light, such as a lamp 81, that the vane 68 is adapted to be motivated into and out of the path of the light impinging on photoelectric cell It in accordance with the deflections of the movable coil thereof and thereby in accordance with the furnace temperature variations. The lamp 6'! is connected to and receives energizing current from the transformer secondary winding 33.

As illustrated, an opaque plate 08. in which a focussing lens 09 is mounted, is also positioned between the photoelectric cell 58 and lamp 81, and the optical system is so arranged that the only light from lamp 61 which is permitted to impinge on cell '58 is that which is transmitted by the lens '8. The lens and the length of the galvanometer pointer 6| are so proportioned that the vane 86 is adapted to move into the path of the light impinging on cell II at the point of focus on the lens 88. Thus, a slight movement of the vane .6 in one direction or the other is E sumcient to fully illuminate ,the cell 59 or to ,cut oil all of the light thereto. In accordance with our present invention, the position of the the photoelectric cell 59. The 1.119 iss'ofcon 68 and lens 89 is adjustable by a solenoid nected in the circuit that thepola rity- ,of ethe potential drop established is thatlshownJjThe energizing circuit for cell 59 may be traced from i the right end terminal of winding 23' to con-; cluster 35, cell 59, conductor 55, resistance 51,

and conductor 43 to the tap 36 on winding 18. The illumination of cell 59 is controlled by the galvanometer 6 in response to variations of the temperature within the furnace I by means which are described hereinafter.

The" adjustable resistance 42 is included in a connection which is common to the grid circuits of both triode sections A and B so that adjust ment thereof operates to simultaneously change the potentials of the grids l6 and 50 relatively to their associated cathodes. It is noted that adjustment of the contact 40 in the direction to include more of the resistance 42 in circuit is 7 effective to render the grids more negative with respect to their associated cathodes while adjustment of the contact 40 in the opposite direction is efiective to render the grids less negative with respect to their associated cathodes. The contact ll desirably is adjusted so as to suit the characteristics of the triode sections A and B to thereby establish the most eflicient operating conditions.

As noted hereinbefore, the illumination of photoeiectric cell 59 and thereby the selective actuation of relays l9 and 20 is controlled by the galvanometer 6, the latter of which in turn isresponsive to changes in the electromotive force produced by thermocouple 2 and thereby is responsive to the temperature variations within furnace I. To this end the galvanometer i is provided with a pointer or needle 60 which is arrangement described hereinafter.

In the preferred embodiment of our invention,

the photoelectric cell 5!, the lamp 61 and the lens 58 are carried by a rotatable casting In which is pivoted for rotation at the left end thereof as seen in Fig. 3. The axis of rotation of the casting 10 is parallel to and is in direct alignment with the axis of rotation of the galvanometer moving coil. The lamp 6! is so positioned that the bulb thereof is in direct alignment with said axes of rotation.

The casting 10 carries an index H at the other end thereof, which index is disposed in cooperative relation with the scale 62. The galvanometer pointer 60 and the vane 06 are so arranged with respect to the casting II and index II that when the temperature of the furnace I is the desired value, the index II will be directly above the index i I along the scale 2. By adjusting the position of the index ll along the scale 62, the temperature maintained in the furnace I, may be controlled as desired. In the embodlment illustrated in Fig. 8 such adjustment is readily effected by manipulation of a knob 12 which is carried on the upper end of a shaft I3. The shaft '13 is mounted in suitable bearings, not shown, and carries a gear I4 which is rigid therewith. The gear is in operative engagement with a circular rack 15, which rack is formed on the end of and is integral with the casting II. The center of the arc of the circular rack 15 coincides with the axis of rotation of casting I. so that on rotation of the knob I! in one direction or the other, clockwise or counter-clockwise movement of the casting II is eifected.

Inthenormaloperationofthesystemthe triodesectionsAandBofvalvellareequally conductive when the illumination of the photoelectric cell II is a predetermined value. Under this condition, the relay coils II and II are equally energized and consequently the motor is not actuated for rotation-in either direction and remains stationary. Upon slight movement of the vane 00, however, for example, in a clockwisedirectioninresponsetoadecreaseinfurnace temperature from the desired value the illumination of photoelectric cell II is substantially increased whereupon the grid II is rendelved less negative in potential with respect to its associated cathode ii and consequently the conductivity of the triode section B is increased. This causes an increase in the energization of relay coil 2| and as a result the relay switch blade is actuated into engagement with the contact 21 to thereby close the energizing circuit for motor held winding [5. The motor I is then operated for rotation in the direction to effect an opening adjustment of the fuel valve 3.

Upon slight movement of the vane 66 in the counter-clockwise direction in response to an increase in furnace temperature from the desired value, the illumination of the photoelectric cell II is substantially decreased, whereupon the grid II is rendered more negative in potential with respect to the cathode ii to thereby reduce the conductivity of the tliode section B. This effects a decrease in the energization of relay coil 2| and consequently actuation of the switch blade 25 into engagement with the contact 26 and thereby closure of the energizing circuit to motor field winding It. The motor I is then actuated in the direction to produce a closing adjustment of the fuel valve I. As noted hereinbefore, rotation of the motor 8 to effect a fuel valve adjustment also effects an adjustment of the follow-up potentiometer l1, It.

It is noted that deflection of the galvanometer pointer Cl in the counter-clockwise direction of an amount to cause the vane 86 to move completely through the light beam and thereby permit illumination of photoelectric cell it even though the furnace temperature is higher than the desired value is prevented by the vane 66 striking against the tapering edge IIB of the casting II.

In accordance with our present invention, adjustment of the follow-up potentiometer l1, l8 eifects an adjustment of the plate 68 and lens it relatively to the lamp 6'! and photoelectric cell It. Such adjustment effects a transverse shift in the focal point of the light beam impinging oncell is relatively to the vane 68, and is in the proper direction, namely toward the left for the case under consideration to restore the illumination of cell It to that value which equalizes the conductivities of the triodes A and B and thereby restores the relay switch arm 25 to a point intermediate the contacts 26 and 21.

In this manner the valve 3 is modulated to an open or closed position in accordance with the decrease or increase respectively of the temtype. and for example, it may be of the type known commercially as mousetrap" relays.

Armature ll carries the plate 08, in which the lens 6| is mounted, and is pivoted for rotation at an intermediate point thereof on a shaft 8|.

The relay'li is mounted on the casting It in any convenient manner and is so arranged that, when deenergiaed, the lens I is in an intermediate position relative to the opening "A in the casting II. The diameter of the opening "A is suitably proportioned relatively to the diameter of the lens ti so as to permit a substantial transverse movement of the lens 9 while still maintaining it all within view of the photoelectric cell it. The shield 68 is provided so as to prevent the passage of light from lamp '1 to cell 59 around the edges of lens $0 and is so proportioned that such leakage of light is not permitted even zhen the lens i! is deflected to its extreme posions.

Armature 19 carries an iron core 82 at one end, which core is adapted to be moved into and out of the coil 11, and carries an iron core 63 at the other end, which core is adapted to be moved into and out of the coil 18. When the relay coils H and I8 are equally energized, the armature It will be maintained in a horizontal position by a spring 84 which is connected at its lower end to a lug 85 formed on the bottom of the relay case 80. The upper end of the spring 84 is connected to member 8| which is riveted to the underside of armature It at the intermediate portion thereof. The member It extends below the shaft ti and is formed as shown in Fig. 4 to accomplish this end.

When one or the other of the relay coils I! or 18 is energized to a greater extent than the other, the armature will be motivated in a counterclockwise or clockwise direction accordingly to thereby shift the position of the lens 69 relatively to the opening 10A in the casting It and consequently to shift the focal point of the light beam directed at the photoelectric cell 59.

Electric power is supplied the relay 16 under control of the follow-up potentiometer ll, it from the transformer secondary winding through a circuit which may be traced from the right end terminal of winding ii to a conductor ll, in which a resistance ll adjustable by a knob 89 is inserted, to the contact I! of the follow-up potentiometer. The left end of resistance II, as seen in Fig. 1, is connected through an adjustable resistance II and the relay coil 11 to a conto the conductor I6 and thereby to the left end terminal of wind ng II. As shown, the resistances 90 and SI are manually adjustable by manipulation of the knob 82. Rotation of the knob 02 in one direction operatu to increase the amount of resistance 90 in circuit and to decrease the amount of resistance II in circuit, and conversely rotation of the knob I! in the opposite direction operates to decrease the amount of resistance II in circuit and to increase the amount of resistance II in circuit.

By reason of the above construction, a true follow-up control system is provided. Upon an increase in temperature of furnace I, the galvanometer pointer I and thereby the vane 66 are actuated in a counter-clockwise direction. Such movement of the vane 6 produces a sharp decrease in the illumination of photoelectric cell It and thereby causes the motor I to be actuated for rotation in the direction to effect a closing zUU" adjushnent of the fuel valve 3. This operation of motor 3 also eifects an adjustment of the contact I! along the follow-up resistance 13 to the right, which adjustment produces an increase in the energization of relay coil I3 and a corresponding decrease in the energization of relay coil 11, whereupon armature I3 is given a rotational adjustment in the clockwise direction about its pivot point against the oppoflng force of spring 34. When the armature 13 has been rotated in the clockwise direction the precise amount to restore the illumination of photoelectric cell to the value at which the triode sections A and B are equally conductive and consequently the relay coils II and are equally energized, the motor 3 is deenergized for rotationandthesystemisstabilized Inthismanner the fuel valve 3 is modulated toward a closed position in accordance with the amount of increase in furnace temperature. The operation of the system on a furnace temperature decrease and thereby on a clockwise movement of vane 66, is similar to that described above except that in this case, the motor I is actuated in the direction to give the fuel valve 3 an opening adjustment and the contact ll an adjustment to the left along resistance l3. This effects a counter-clockwise adjustment of the armature I3, against the opposing force of the spring 34, of an amount sufficient to restore the illumination of the photoelectric cell 59 to the value at which the motor 9 is deenergized, thereby stabilizing the system. The valve 3 is thus modulated to an open position in accordance with the amount of decrease in furnace temperature.

The provision of the adjustable resistance 88 in the energizing circuit to the coils I1 and 18 of relay l6 permits adjustment of the throttlin range of the system whereby the extent to which the fuel valve'3 is adjusted in response to a given change in furnace temperature may be varied. For example, upon an adjustment of resistance 38 decreasing the amount of said resistance in circuit, the voltage applied to the follow-up arrangement in will be increased whereby a smaller adjustment of the contact I! along resistance l8 will be required to effect the followup actuation of relay 16 and lens 69 required to restore the illumination of photoelectric cell 59 to the value at which the motor 9 is deenergized for rotation. Accordingly a smaller fuel valve adjustment will be made for a given furnace temperature change. Conversely, on an adjustment of resistance 88 increasing the amount of said resistance in circuit, the voltage applied to the follow-up arrangement III will be decreased whereby a larger adjustment of the contact I! along resistance l8 will be required to effect the required follow-up actuation of lens 69 needed to deenergize motor 9. With this adjustment of resistance 38, a larger fuel valve adjustment will be made for a given furnace temperature change. The knob 89 is provided in order to facilitate the adjustment of resistance 38.

The provision of the adjustable resistances and SI in the follow-up arrangement it permits a so-called reset" adjustment of the system so that on a change in the operating condition of the furnace I, for example, on a change in the load thereof, or on a change in the B. t. 11. content of the fuel being supplied thereto. the tendency of said load change fuel heating valve change, or other operating condition change, to

' increase or decrease the furnace temperature may be neutralized. As explained hereinbefore,

U i\UOO Li LHLHUL the resistances lliand ll areadaptedtobe simultaneously adjusted in opposite directions by manipulation of the knob 32. Such manipulation of knob 32 operates to change the position of relay armature II, and thereby the position of lens 38, for a given position of contact ll along resistance l3, and thereby operates to change the relation between the position of the lens 33 and the adjustment of fuel valve 3 for a given furnace temperature value at which the motor 8 is not energized for rotation in either direction.

- Accordingly, on such manipulation, the motor I is energized for rotation to effect an adjustment of fuel valve 3 and an adjustment of contact ll along resistance I3 as required to restore the lens 9 to the position in which the motor 3 is deenergized for rotation Thus, the provision of resistances 30 and Ii permits load compensating or "rese adjustments to be readily made.

As will be apparent to those skilled in the art, the provision of the adjustable resistances 33, and SI permits of a wide range of variation in the furnace operating characteristics thereby permitting a desirably good regulation under very different conditions of operation.

In Fig. 5 I have illustrated, more or less diagrammatically, a modification of the relay 16. As illustrated, the relay arrangement of Fig. 5 includes a U-shaped member 93 of magnetic material, on one leg of which a relay coil I1 is wound and on the other leg of which the relay coil 18 is wound, An elongated flexible member 94 is disposed between the legs of the member 93 and has one end rigid with the closed end of member 83, as seen in the drawings. The other end of member 34 extends between the open ends of member 83. When the relay coils TI and 13 are equally energized the member 34 is intermediate the legs of member 83, but when One relay coil IT or 18 is energized to a greater extent than the other, the flexible member 84 is deflected toward the leg of member 33 carrying that coil. The extent of deflection of member 34 is in accordance with the difference in energization of the relay coils I1 and 18. The plate 68 and lens 69 are mounted on the deflecting end of member 84 so that on the deflection of the latter, the plate 68 and lens 69 are given corresponding adjustments. This relay may be mounted in any suitable manner on the casting 10.

While in accordance with the provisions of the statutes, we have illustrated and described the best form of our invention now known to us, it will be apparent-to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of our invention as set forth in the appended claims, and that in some cases certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In a control system, a device to be adjusted in a plurality of positions for controlling the value of a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, means responsive to changes in the magnitude of said condition, a device under control of said last mentioned means adapted to effect a control action of said radiant energy path and thereby adapted to responsive means, a power actuated device to position said first mentioned device, means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation oi said radiant energy responsive means in one sense and to actuate said power actuated device in the other direction upon actuation oi said radiant energy responsive means in the opposite sense, and means mechanically independent oi said radiant energy responsive means and operated by said power actuated device to an extent proportional to the magnitude oi the control action on said radiant energy path produced by said second mentioned device to neutralize the effect said control action on said radiant energy path whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition.

2. In a control system, a device to be adiusted in a plurality oi positions for controlling the value of variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, voltage producing means responsive to changes in the magnitude oi said condition, a galvanometer under control of said last mentioned means adapted to effect a control action on said radiant energy path and thereby adapted to control the actuation oi said radiant energy responsive means, a power actuated device to position said first mentioned device, means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation oi said radiant energy responsive means in one sense and to actuate said power actuated device in the other direction upon actuation oi said radiant energy responsive means in the opposite sense, and means mechanically independent of said radiant energy responsive means and operated by said power actuated device to an extent proportional to the magnitude oi the control action on said radiant energy path produced by said galvanometer to neutralize the effect oi said control action on said radiant energy path whereby said first mentioned device is positioned proportionally to the change in magnitude oi said condition.

3. In a control system, a device to be adjusted in a plurality oi positions ior controlling the value oi a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, means responsive to changes in magnitude oi said condition, a device under control oi said last mentioned means adapted to effect a control action on said radiant energy pathand thereby adapted to control the actuation of said radiant energy responsive means, a reversible electrical motor to position said first mentioned device, means controlled by said radiant energy responsive means to selectively energize said reversible electrical motor for rotation in one direction or the other upon actuation of said radiant energy responsive means in one sense or in the opposite sense, and means mechanically independent of said radiant energy responsive means and operated by said reversible electrical motor to an extent pro portional to the magnitude oi the control action on said radiant energy path produced by said second mentioned device to neutralize the eiiect oi said control action on said radiant energy path whereby said first mentioned device is positioned proportionally to the change in magnltude oi said condition.

4. In a control system, a device to be adJusted in a plurality of positions for controlling the value oi a variable condition, means to produce a path oi radiant energy, means responsive to said radiant energy path, voltage producing means responsive to changes in the magnitude of said condition, a galvanometer under control oi said last mentioned means adapted to effect a control action on said radiant energy path and thereby adapted to control the actuation of said radiant energy responsive means, a reversible electrical motor to position said first mentioned device, means controlled by said radiant energy responsive means to selectively energize said reversible electric motor ior rotation in one direction or the other upon actuation of said radiant energy responsive means in one sense or in the opposite sense, and means mechanically independent oi said radiant energy responsive means and operated by said reversible electric motor to an extent proportional to the magnitude of the control action on said radiant energy path produced by said galvanometer to neutralize the eiiect oi said control action on said radiant energy path whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition.

5. In a control system, a device to be adjusted in a plurality of positions for controlling the value oi a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, means responsive to changes in th magnitude of said condition, a device under control of said last mentioned means adapted to efi'ect a control action on said radiant energy path and thereby adapted to control the actuation of said radiant energy responsive means, a power actuated device to position said first mentioned device, an electrical network controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation of said radiant energy responsive means in one sense and to actuate said power actuated device in the other direction upon actuation of said radiant energy responsive means in the opposite sense, and means mechanically independent of said radiant energy responsive means and operated by said power actuated device to an extent proportional to the magnitude of the control action on said radiant energy path produced by said second mentioned device to neutralize the effect of said control action on said radiant energy path whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition.

6. In a control system, a device to be adjusted in a plurality of positions for controlling the value oi a variable condition, means to produce a path oi radiant energy, means responsive to said rariant energy path, voltage producing means responsive to changes in the magnitude of said condition, a galvanometer under control of said last mentioned means adapted to effect a control action on said radiant energy path and thereby adapted to control the actuation of said radiant energy responsive means, a power actuated device to position said first mentioned device, a normally stabilized electrical network which is adapted to be unstabilized under control oi said radiant energy responsive means to actuate said power actuated device in one direction upon unstabilization thereoi in one sense and to actuate said power actuated device in the other direction upon unstabilization thereof in the opposite sense diant ener y and means mechanically independent of said radiant energy responsive means and operated by said reversible motor to an extent proportional to the magnitude of the control action on said radiant energy path produced by said galvanometertoneutralisetheefiectotsaidcontrol actiononsaidradiantenergypathwherebysaid first mentioned device is positioned proportionally to the change of magnitude oi. said condition.

7.Inacontrolsystem,adevicetobeadjusted in a plurality of positions for controlling the value of a variable condition, means to produce a path of radiant energy, 'means responsive to said radiant en rgy P th, voltage producing means responsive to changes in the magnitude oi said condition, a galvanometer under control oi said last mentioned means adapted to eflect a control action on said radiant energy Pith and thereby adapted to control the actuation of said radiant energy responsive means, a reversible electrical motor to position said first mentioned device, a normally stabilised electrical network which is adapted to be unstabilized under control of said radiant energy responsive means to selectively energize said reversible electrical motor for rotation in one direction or the other upon unstsbilization thereof in one sense or in the opposite sense, and means mechanically independent of said radiant energy responsive means and operated by said reversible motor to an extent proportional to the magnitude of the control action on said radiant energy path produced by said galvanometer to neutralize the eflect of said control action on said radiant energy path whereby said first mentioned device is positioned proportionally to the change of magnitude of said condition.

8. In a control system, a device to be adjusted in a plurality of positions for controlling the value of a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, means responsive to changes in the magnitude of said condition} deflectable member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means inaccordance with the position thereof relatively to said radiant energy path, a device under control of said condition responsive means to vary the relative positions said deflectable member and said radiant ener y path, a power actuated device to position said first mentioned device, means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation of said radiant energy responsive means in one sense.

and to actuate said power actuated device in the other direction upon actuation of said radiant energy responsive means in the oppomte sense, and means operated by said powerv actuated derespomive to changes in the magnitude of said condition, a defiectable member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means in accordance with the position thereoi relatively to said radiant energy path, a galvanometer under control oi said condition responsive means to vary the relative positionsoisaiddefiectablememberandsaidradiant energypath,apoweractuated devicetoposition said first mentioned device, means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation oi said radiant energy responsive means inonesenseandtoactuatesaidpoweractuated device in the other direction upon actuation of saidradiantenergyresponsivemeansintheopposite sense, and means operated by said power actuated device to an extent proportional to the magnitude of the control eflect on said radiant energy Path produced by said deflectable member to restore the original relative positions oi said defiectable member and said radiant energy path to thereby neutralize the eilect oi the control action on said radiant energy responsive means eflected by said galvanometer whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition.

10. In a control system, a device to be adjusted in a plurality of positions for controlling the value of a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, voltage producing means responsive to changes in the magnitude of said condition, a defiectable member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means in accordance with the position thereof relatively to said radiant energy path, a galvanometer imder control of said condition responsive means to vary the relative positions 01! said defiectable member and said radiant energy path, a reversible electrical motor to position said first mentioned device, a normally stabilized electrical network adapted to be unstabillzed under control of said radiant energy responsive means and adapted when unstabilized in one sense to actuate said reversible electrical vice to'an extent proportional to the magnitude oi the control etlect on said radiant energy P th produced by said defiectable member to restore the original relative postions of said defiectable member and said radiant energy Path to thereby neutralize the effect of the control action on said radiant energy responsive means effected by said second mentioned device whereby said first mentioned device is positioned proportionally-to the change in magnitude of said condition.

-9. In a control system, a device to-be adjusted in-a plurality of positions ior controlling the value oi s variable condition, means to produce apath of radiant energy, means resp to Said 1' ath, voltage producing, means motor in one direction and adapted when unstabilized in the opposite sense to actuate said reversible electrical motor in the other direction, and means operated by said reversible electrical motor to an extent proportional to the magnitude of the control effect on said radiant energy path produced by said defiectable member to restore the original relative positions 01 said defiectable member and said radiant energy path to thereby neutralize the effect of the control action on said radiant energy responsive means efiected by said galvanometer whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition. I

'11. 'In a control system, a device to be adjusted in a plurality of positions for controlling the value of ,a variable condition, means to produce a path of radiant ener y. means responsive to said radiant energypath. means responsive to changes in the magnitude of saidcondition, a

"diant energy impinging on said radiant energy j responsive means in accordance with the position thereof relatively to said radiant energy path, a

device under control of-said condition responsive meansto vary the relative positions or said deflectablememberandsaidradiantenergypatna poweractuateddevlcetopositionsaidfirstmentinned device, means controlled by said radiant energyresponsivemeanstoactuatesaidpower actuated device in one direction upon actuation oi-saidradiantenergyresponsivemeansinone aenseandtoactuatesaidpoweractuateddevice intheotherdirectionuponactuationoisaid 'radiantenergyresponsivemeansintheopposite sense, an electrical network adapted to be adjusted by said power actuated device, and means controlled by said electrical network to restore the original relative positions of said defiectable member and said radiant energy path to thereby neutralize the effect of the control action on said radiant energy responsive means eflected by said second mentioned device whereby said first mentioned device is positioned prop rtionally to the change in magnitude of said condition.

12. In a control system, a device to be adimted in a plurality positions for controlling the value of a variable condition, means to produce a path of radiant energy. means responsive to said radiant energy path, means responsive to changes in the magnitude or said condition, a deflectable member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means in accordance with the position thereof relatively to said radiant energy path. a device under control of said condition responsive means to vary the relative positions of said defiectable member and said radiant energy path, a power actuated device to position said first mentioned device, means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation of said radiant energy responsive means in one sense and to actuate said power actuated device in the other direction upon actuation of said radiant energy responsive means in the opposite sense, an electrical network adapted to be adjusted by said power actuated device, means controlled by said electrical network to restore the original relative positions of said defiectable member and said radiant energy path to thereby neutralize the eifect oi the control action on said radiant en r y responsive means eil'ected by said second mentioned device whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition, and means to adjust said electrical network to vary the efiect on said electrical network of a given adjustment thereof by said power actuated device.

13. In a control system, a device to be adjusted in a plurality of positions torcontrolling the value of a variable condition, means to produce a path of radiant energy, means respomive to said radiant energy P h, voltage producing means responsive to changes in the magnitude of said condition, a defiectable member disposed in the path 0! said radiant energy and adapted to control the radiant energy impingint on said radiant energy responsive means in accordance with the position thereof relatively to said radiant energy path, a galvanorneter under control of said condition responsive means to vary the relative positions of said defiectable member and said radiant energy path, a reversible electrical motor to position said first mentioneddevice, means controlled by said radiant energy responsive means to actuate said reversible electrical motor in one direction upon actuation of said radiant energyrespomivemeansinonesenseand to actuate said reversible electrical motor in the other direction upon actuation of said radiant energyresponsivemeansintheoppositcsensaan electrical network adapted to be adjusted by said reversible motor, means controlled by said electrical network to restore the original relative positions or said defiectable member and said radiant energy p th to thereby neutralize the effect 01 the control action on said radiant energy responsive means efiected by said galvanometer whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition, and means to adjust said electrical network to vary the effect on said electrical network of a given adjustment thereof by said motor.

14. In a control system, a device to be adjusted in a plurality oi! positions for controlling the value of a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, means responsive to changes in the magnitude of said condition, a deflect-able member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means in accordance with the position thereof relatively to said radiant energy path, a device under control of said condition responsive means to vary the relative positions of said deflectable member and said radiant energy path, a power actuated device to position said first mentioned device, means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation of said radiant energy responsive means in one sense and to actuate said power actuated device in the other direction upon actuation of said radiant energy responsive means in the opposite sense, an electrical network adapted to be adjusted by said power actuated device, means controlled by said electrical network to restore the original relative positions 0! said deflectable member and said radiant energy path to thereby neutralize the eiIect of the control action on said radiant energy responsive means eflected by said second mentioned device whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition, and means to adjust said electrical network to vary the control oi said controlled means by said electrical network.

15. In a control system, a device to be adjusted in a plurality of positions for controlling the value of a variable condition, means to produce a path or radiant energy. means responsive to said radiant energy .path, voltage producing means responsive to changes in the magnitude oi said condition, a defiectable member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means in accordance with the position thereof relatively to said radiant energy path, a galvanometer under control of said condition responsive means to vary the relative positions of said defiectable member and said radiant energy path, a reversible electrical motor to position said first mentioned device, means controlled by said radiant energy responsive means to actuate said reversible electrical motor in one direction upon actuation oi said radiant energy responsive means in one sense and to actuate said reversible electrical motor in the other direction upon actuation of said radiant energy responsive means in the opposite sense, an electrical network adapted to be adjusted by said reversible electrical motor, means controlled by said electrical network to restore the original relative positions of said defiectable member and said radiant energy path to thereby neutralize the effect of the control action on said radiant energy responsive means effected by said galvanometer whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition, and means to adjust said electrical network to vary the control of said controlled means by said electrical network.

16. In a control system, a device to be adjusted in a plurality of positions for controlling the value of a variable condition, means to produce a path of radiant energy, means responsive to said radiant energy path, means responsive to changes in the magnitude of said condition, a defiectable member disposed in the path of said radiant energy and adapted to control the radiant energy impinging on said radiant energy responsive means in accordance with the position thereof relatively to said radiant energy path, a device under control of said condition responsive means torvary the relative positions of said deflectahie member and said radiant energy path, a power actuated device to position said first mentioned device. means controlled by said radiant energy responsive means to actuate said power actuated device in one direction upon actuation of said radiant energy responsive means in one sense and to actuate said power actuated device in the other direction upon actuation of said radiant energy responsive means in the opposite sense, an electrical network adapted to be adjusted by said power actuated device. difierential relay means controlled-by said electrical network to restore the original relative positions of said defiectable member and said radiant energy path to thereby neutralize the eiiect of the control action on said radiant energy responsive means eifected by said second mentioned device whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition, impedance means connected in said network and adaptedtobeadjustedtovarythecontrolof said diiferentlal relay means by said electrical network, and other impedance means connected in said network and adapted to be adjusted to vary the efiect on said electrical network of a iven adjustment thereof by said power actuated device.

17. In a control system, a device to be adjusted in a plurality of positions for mntroiling the value of a variable condition, means to produce a light beam, a light sensitive device responsive to said light beam, means responsive to changes in the magnitude of said condition, a defiectable memberdisposedinthepathofsaidlightbeam and adapted to control the illumination of said light sensitive device in accordance with the position thereof. relatively to said li ht beam, a device imder control of said condition responsive means to vary the relative positions of said defiectablememberandsaidlightbeamapower actuated device to position said first mentioned device, means controlled by said light sensitive devicetoactustesaidpoweractuateddevicein one direction upon an increase in the illumination thereof from a predetermined value and to actuatesaidpoweractuateddeviceintheother direction upon a decrease in the illumination of said light sensitive device from said predetermined value, and means operated by said power actuated device to an extent proportional to the magnitude of the control effect on said light beam produced by said defiectable member to restore the original relative positions of said defiectable member and said light beam to thereby neutralize the effect of the control action on said light sensitive device eifected by said third mentioned device whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition.

18. In a control system, a device to be adjusted in a plurality of positions for controlling the value of a variable condition, means to produce a beam of light. a light sensitive device adapted to be illuminated by said light beam, means responsive to changes in the magnitude of said condition, a device under control of said last mentioned means adapted to efi'ect a control action on said light beam and thereby adapted to control the illumination of said light sensitive device, a power actuated device to position said first mentioned device, means controlled by said light sensitive device to actuate said power actuated device in one direction upon an increase in illumination of said light sensitive device from a predetermined value and to actuate said power actuated device in the other direction upon a decrease in the illumination of said light sensitive device from said predetermined value. and means mechanically independent of said light sensitive device operated by said power actuated device to an extent proportional to the magnitude of the control action m said light beam produced by said third mentioned device to neutralize the effect of said control action on said light beam whereby said first mentioned device is positioned proportionally to the change in magnitude of said condition.

19. In a control system, a device to be adjusted in a plurality of positions for controlling the value oi a variable condition, means to produce a light beam, a light sensitive device adapted to be illuminated by said light beam, voltage producing means responsive to changes in the magnitude of said condition. a galvanometer under control of said last mentioned means adaptedtoefiectacontrolactiononsaidlightbeam and thereby adapted to control the illumination of said light sensitive device. a reversible electrleal motor to position said first mentioned device, a normally stabilized electrical network which is adapted to be unstabilized under control of said light sensitive device to selectively energise said reversible electrical motor for rotation in one direction or the other upon unstabilizationthereofinonesenseorinthe oppoaitesense,

o and means mechanically independent of said light sensitive device operated by said reversible motor to an extent proportional to the magnitudeofthecontrol actiononsaid light beamproduced by said galvanometer to neutralize the effect of said control action on said light beam whereby said first mentioned device is positioned proportionally to the change of magnitude of said condition.

. R0800! D. BEAN. 8483! B. JONES, 

